1. Field of the Invention
This invention relates to the field of metal fusion bonding, and more particularly, to preplacing a quantity of unfused solid filler onto a target device, such as a Ball Grid Array (BGA), prior to applying fusing heat and prior to juxtaposing parts to be joined. The unfused solid filler has a particular size and shape, more specifically, that of a solder ball.
2. Description of the Related Art
Devices that dispense solder balls through mechanical means are well known. Solder balls are used for attaching BGAs to printed circuits. For BGAs, a typical solder ball has a diameter of 30 mils. Solder balls are also used for attaching flip chips to integrated circuit packages. For flip chips, a typical solder ball has a diameter of 10-20 mils. As microelectronics become smaller, the size of solder balls for such microelectronics also becomes smaller.
Disadvantageously, all known prior art solder ball dispensing devices use, at least in part, mechanical parts such as levers, to transport solder balls through the prior art devices and/or to eject them out of the prior art devices. Known dispensing devices have a problem of solder balls sticking to mechanical parts that move the solder balls through such dispensing devices, thereby jamming the dispensing device. A solder ball sticks to a mechanical part as a result of a cold weld bond to a metallic component or as a result of static electricity. As solder balls become smaller, the probability of a cold weld bond of a solder ball to a metallic component occurring becomes greater. As solder balls become smaller, the effect of static electricity on the solder balls becomes more pronounced.
As solder balls become smaller, the levers that move the solder balls have to be machined to higher tolerances, thereby making them more expensive. When a dispensing device has a plurality of small mechanical parts that work together, their tolerances are cumulative, thereby disadvantageously requiring even higher tolerances. Also, as levers become smaller, the lack of strength of the levers becomes a problem. Furthermore, proportionately scaled down versions of devices, such as solenoids, which actuate levers, are not always available.
Most known prior art solder ball dispensing devices utilize solely mechanical parts; however, a few known dispensing devices utilize, in part, gas pressure and vacuum to move solder balls through the device. Examples such of known devices are:
U.S. Pat. No. 5,279,045, issued Jan. 18, 1994, to Odashima et al., entitled Minute Particle Loading Method and Apparatus uses a fluid to stir up minute particles in an enclosed space. However, Odashima, et al., has no provision for dispensing solder balls one at a time.
U.S. Pat. No. 5,431,332, issued Jul. 11, 1995, to Kirby et al., entitled Method and Apparatus for Solder Sphere Placement Using an Air Knife directs a column of air across a surface of a stencil to remove excess solder balls. However, Kirby, et al., has no provision for dispensing solder balls one at a time.
U.S. Pat. No. 5,626,277, issued May 6, 1997, to Kawada entitled Mounting Apparatus of Solder Balls has a ball suction jig that uses vacuum for collecting solder balls and a blow gas for agitating solder balls in a ball feed jig. However, Kawada has no provision for dispensing solder balls one at a time.
U.S. Pat. No. 5,878,911, issued Mar. 9, 1999, to Lin et al., entitled Solder-Ball Supplying Apparatus discloses vacuum means used to suck out a preset amount of solder balls from a storage tank. However Lin et al., uses a valve to control the flow of solder balls through the apparatus.
U.S. Pat. No. 6,003,753, issued Dec. 21, 1999, to Hwang et al., entitled Air-Blow Solder Ball Loading System for Micro Ball Grid Arrays applies fluid pressure to solder balls within a tub to force the solder balls to float on gas pressure toward a vacuum head that includes vacuum apertures for picking up solder balls from the tub. However, Hwang et al., has no provision for dispensing solder balls one at a time.
U.S. Pat. No. 6,182,356, issued Feb. 6, 2001, to Bolde entitled Apparatus for Solder Ball Mold Loading has an air supply line connected to a reservoir and blowing air onto solder balls in the reservoir to break up accumulation of solder balls at the bottom of the reservoir, and a vacuum for facilitating reception of the solder balls into cavities of a mold. However, Bolde accomplishes dispensing of individual solder balls by mechanical movement of a feeder exit port across the mold.
U.S. Pat. No. 6,227,437, issued May 8, 2001, to Razon et al., entitled Solder Ball Delivery and Reflow Apparatus and Method of Using the Same uses a pressurized fluid that is introduced into a reservoir to urge a continuous flow of solder material through a feed tube from the reservoir to a capillary. The capillary deposits one solder ball at a time onto a substrate. However, the capillary uses a mechanical indexing slide mechanism to select one solder ball at a time.
U.S. Pat. No. 6,244,788, issued Jun. 12, 2001, to Hernandez entitled Apparatus for Supplying Solder Balls uses a fluid to actuate a continuous flow of solder balls from a reservoir to a receptacle. However, Hernandez does not disclose dispensing solder balls one at a time.
U.S. Pat. No. 6,325,272, issued Dec. 4, 2001, to May et al., entitled Apparatus and Method for Filling a Ball Grid Array uses air to force solder balls into and out of holes of a BGA template. However, May et al., does not disclose any method or apparatus for transferring solder balls to the BGA template.
U.S. patent application Publication No. 2002/0088843 A1, by Saso, published Jul. 11, 2002, entitled Solder Ball Pitcher is a device for supplying a series of individual solder balls in which solder balls are moved by solid mechanical components which also move. However, Saso does not disclose movement of solder balls as a result of application of vacuum or air pressure.
U.S. patent application Publication No. 2002/0135064 A1, by Hazeyama et al., published Sep. 26, 2002, entitled Transfer Apparatus for Arraying Small Conductive Bumps on Substrate and/or Chip has a vacuum source, and a pallet for holding solder balls in a same pattern as a pattern of conductive pads on a semiconductor chip, and uses air to push the array of conductive balls sidewards and to make the array of conductive balls float from the pallet to the semiconductor chip. However, Hazeyama et al., does not disclose any method or apparatus for transferring solder balls to the array.
Thus, what is needed is a solder ball dispenser for dispensing solder balls to BGAs, which overcomes the disadvantages of the prior art by using only air pressure and vacuum to move solder balls through the solder ball dispenser. What is also needed is a solder ball dispenser for dispensing solder balls to BGAs that can be easily scaled down to dispense smaller solder balls to flip chips.
Briefly described, and in accordance with a preferred embodiment thereof, the present invention relates to an apparatus for dispensing a series of single solder balls, which includes a curved chamber for containing a multiplicity of solder balls set in motion by gas flowing within the curved chamber, an elongate chamber having a first end and a second end, and an ejector connected to the second end of the elongate chamber. The first end of the elongate chamber connected to the curved chamber for receiving solder balls from the curved chamber. The elongate chamber is sized to accept a single line of solder balls. The ejector receives the single line of solder balls and, in response to application of gas pressure and vacuum on the solder balls, dispenses a series of single solder balls. All movement of solder balls within the apparatus is caused only by application of gas pressure and vacuum.
The present invention also relates to an apparatus for dispensing a series of single solder balls, which includes a substantially circular chamber having a depth of approximately the diameter of the solder balls. The chamber has an opening for delivering blowing gas into the chamber for setting the solder balls within the chamber in motion, and a buffer chute for allowing one solder ball at a time to escape, against gravity, from the chamber as a result of the motion of the one ball, and for temporarily storing a single line of solder balls from which the balls are dispensed.
The present invention further relates to an apparatus for dispensing a series of single solder balls. The apparatus includes an elongate chamber holding a single line of solder balls, and a pneumatic singulator connected to the elongate chamber. The pneumatic singulator receives the single line of solder balls. The pneumatic singulator has a channel for the balls. The channel has a plurality of openings for application of cycles of alternate gas pressure and vacuum to the channel. Each half cycle causes at least one solder ball from the single line of solder balls to move from one of the plurality of openings to another of the plurality of openings.
The present invention further relates to an apparatus for ejecting a series of single solder balls, which includes an elongate chamber holding a single line of solder balls and also includes a pneumatic singulator connected to the elongate chamber. The pneumatic singulator receives the single line of solder balls. The pneumatic singulator has a channel for the balls. The channel has a plurality of bends. The channel has a plurality of openings at which one of gas pressure and vacuum is applied to move solder balls through the channel. The balls pause at each bend of the channel prior to being ejected one at a time from the apparatus.
The present invention further relates to a method of organizing solder balls into a single line, which includes the steps of swirling a multiplicity of solder balls in a first curved chamber that has a size substantially larger than a solder ball diameter in all three dimensions; transferring at least some of the multiplicity of solder balls into a second chamber that has a size substantially larger than a solder ball diameter in only two dimensions and a size approximately of a solder ball diameter in the third dimension; swirling the at least some of the multiplicity of solder balls in the second curved chamber; and transferring a plurality of the at least some of the multiplicity of solder balls into an elongate chamber that has a size substantially larger than a solder ball diameter in only one dimension and a size approximately of a solder ball diameter in two dimensions.
The present invention further relates to a method of dispensing solder balls that comprises the steps of (a) receiving a single line of solder balls; (b) transferring each solder ball from the single line of solder balls into a pneumatic singulator; (c) moving each solder ball through the pneumatic singulator using only vacuum and gas pressure; (d) causing each solder ball to pause at least two times while moving through the pneumatic singulator; (e) causing each solder ball to change trajectory by at least 45xc2x0 after each pause; and (f) ejecting, one at a time, each solder ball out of the pneumatic singulator.
The present invention further relates to a method of dispensing solder balls that comprises the steps of (a) swirling a multiplicity of solder balls in a first curved chamber, in which the first curved chamber has a size substantially larger than a solder ball diameter in all three dimensions; (b) transferring at least some of the multiplicity of solder balls into a second chamber, in which the second chamber has a size substantially larger than a solder ball diameter in only two dimensions and having a size approximately of a solder ball diameter in the third dimension; (c) swirling the at least some of the multiplicity of solder balls in the second curved chamber; (d) transferring a plurality of the at least some of the multiplicity of solder balls into an elongate chamber, in which the elongate chamber has a size substantially larger than a solder ball diameter in only one dimension and has a size approximately of a solder ball diameter in two dimensions; (e) transferring the plurality of the at least some of the multiplicity of solder balls into a pneumatic singulator; and (f) ejecting, one at a time, each solder ball of the plurality of the at least some of the multiplicity of solder balls out of the pneumatic singulator.